Angular momentum of spiral galaxies. II. Detailed models and correlations for 17 galaxies

The rotation curve analysis method of the previous paper (Nordsieck, Paper I) has been used to calculate the mass-surface-density distribution in 17 spiral galaxies. The assumption of constant MIL ratio in the outer disk region is verified, which allows the use of an exponential density extrapolation to estimate the total mass, kinetic energy, and angular momentum of these systems, along with their probable errors. The mass and angular momentum are shown to be completely specified by two independent observable parameters, a characteristic velocity and radius. However, it can be shown statistically that observational errors in these quantities can lead to a very tight power- law relationship between the mass and angular momentum, which may have no connection with the "true" relationship. The sample of the present paper and of similar investigations by previous authors all lead to this same spurious power law. Comparison, instead, of the characteristic radii and velocities of galaxies is more informative and less subject to statistical bias. There is a good correlation between the M/L ratio and the B - V color or Yerkes type seen in this sample, but no significant correlation with the morphological type. Similar correlations using the mass or angular momentum are noted, but these are not physically significant because observational selection of very luminous galaxies creates a false correlation between mass and M/L. Subject headings: galaxies - galaxies, motions in - mass luminosity relation